From 5a07fd8932b9c8573d3ef56cb84fc0a6479f6372 Mon Sep 17 00:00:00 2001
From: nemunaire <nemunaire@nemunai.re>
Date: Thu, 26 May 2022 05:44:04 +0200
Subject: [PATCH] Add new rewrite rule to decode base64 content

---
 reader/rewrite/rewrite_functions.go | 30 +++++++++++++++++++++++++++++
 reader/rewrite/rewriter.go          |  6 ++++++
 reader/rewrite/rewriter_test.go     | 30 +++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)

diff --git a/reader/rewrite/rewrite_functions.go b/reader/rewrite/rewrite_functions.go
index b5b52409..20e2c5d9 100644
--- a/reader/rewrite/rewrite_functions.go
+++ b/reader/rewrite/rewrite_functions.go
@@ -5,6 +5,7 @@
 package rewrite // import "miniflux.app/reader/rewrite"
 
 import (
+	"encoding/base64"
 	"fmt"
 	"html"
 	"net/url"
@@ -288,3 +289,32 @@ func addCastopodEpisode(entryURL, entryContent string) string {
 
 	return player + `<br>` + entryContent
 }
+
+func applyFuncOnTextContent(entryContent string, selector string, repl func(string) string) string {
+	var treatChildren func(i int, s *goquery.Selection)
+	treatChildren = func(i int, s *goquery.Selection) {
+		if s.Nodes[0].Type == 1 {
+			s.ReplaceWithHtml(repl(s.Nodes[0].Data))
+		} else {
+			s.Contents().Each(treatChildren)
+		}
+	}
+
+	doc, err := goquery.NewDocumentFromReader(strings.NewReader(entryContent))
+	if err != nil {
+		return entryContent
+	}
+
+	doc.Find(selector).Each(treatChildren)
+
+	output, _ := doc.Find("body").First().Html()
+	return output
+}
+
+func decodeBase64Content(entryContent string) string {
+	if ret, err := base64.StdEncoding.DecodeString(strings.TrimSpace(entryContent)); err != nil {
+		return entryContent
+	} else {
+		return html.EscapeString(string(ret))
+	}
+}
diff --git a/reader/rewrite/rewriter.go b/reader/rewrite/rewriter.go
index feb0139e..b00ea1a1 100644
--- a/reader/rewrite/rewriter.go
+++ b/reader/rewrite/rewriter.go
@@ -102,6 +102,12 @@ func applyRule(entryURL, entryContent string, rule rule) string {
 		}
 	case "add_castopod_episode":
 		entryContent = addCastopodEpisode(entryURL, entryContent)
+	case "base64_decode":
+		if len(rule.args) >= 1 {
+			entryContent = applyFuncOnTextContent(entryContent, rule.args[0], decodeBase64Content)
+		} else {
+			entryContent = applyFuncOnTextContent(entryContent, "body", decodeBase64Content)
+		}
 	}
 
 	return entryContent
diff --git a/reader/rewrite/rewriter_test.go b/reader/rewrite/rewriter_test.go
index f796da7d..fab7da26 100644
--- a/reader/rewrite/rewriter_test.go
+++ b/reader/rewrite/rewriter_test.go
@@ -295,3 +295,33 @@ func TestRewriteAddCastopodEpisode(t *testing.T) {
 		t.Errorf(`Not expected output: got "%s" instead of "%s"`, output, expected)
 	}
 }
+
+func TestRewriteBase64Decode(t *testing.T) {
+	content := `VGhpcyBpcyBzb21lIGJhc2U2NCBlbmNvZGVkIGNvbnRlbnQ=`
+	expected := `This is some base64 encoded content`
+	output := Rewriter("https://example.org/article", content, `base64_decode`)
+
+	if expected != output {
+		t.Errorf(`Not expected output: got "%s" instead of "%s"`, output, expected)
+	}
+}
+
+func TestRewriteBase64DecodeInHTML(t *testing.T) {
+	content := `<div>Lorem Ipsum not valid base64<span class="base64">VGhpcyBpcyBzb21lIGJhc2U2NCBlbmNvZGVkIGNvbnRlbnQ=</span></div>`
+	expected := `<div>Lorem Ipsum not valid base64<span class="base64">This is some base64 encoded content</span></div>`
+	output := Rewriter("https://example.org/article", content, `base64_decode`)
+
+	if expected != output {
+		t.Errorf(`Not expected output: got "%s" instead of "%s"`, output, expected)
+	}
+}
+
+func TestRewriteBase64DecodeArgs(t *testing.T) {
+	content := `<div>Lorem Ipsum<span class="base64">VGhpcyBpcyBzb21lIGJhc2U2NCBlbmNvZGVkIGNvbnRlbnQ=</span></div>`
+	expected := `<div>Lorem Ipsum<span class="base64">This is some base64 encoded content</span></div>`
+	output := Rewriter("https://example.org/article", content, `base64_decode(".base64")`)
+
+	if expected != output {
+		t.Errorf(`Not expected output: got "%s" instead of "%s"`, output, expected)
+	}
+}